EP0435956B1 - Catalyst with a double casing system - Google Patents

Abstract

Double casing system for catalysts, in particular for the catalysts of passenger vehicles with spark-ignition engines and high operational capacity. Two metallic honeycomb elements (1, 2) with their internal steering column jackets (3, 4) are preferably arranged within an external steering column jacket (8), whereby only one of the end areas (12, 13) of each internal steering column jacket (3, 4) is mounted (10, 11) on the external jacket (8), their internal parts being axially mobile and sliding into each other, thus forming a sliding fit (5). Because of its gap space (9), the double casing system acts as a thermal insulation. Radial thermal tensions between the honeycomb elements (1, 2) and the internal steering column jackets (3, 4) are thereby reduced while axial thermal dilatation because of the sliding fit (5) does not cause any tensions.

Description

The present invention relates to a coated catalytic converter, in particular for motor vehicles, which contains at least one metallic honeycomb-shaped catalyst carrier body which is permeable to exhaust gas and has a jacket tube carrying the latter.

Metallic catalyst carrier bodies are known in numerous forms, for example from EF-A-0 245 737. They can, for example, be constructed from sheet steel or else be produced by powder metallurgy. Of particular importance for the durability of such a body is the control of the mechanical stresses caused by thermal alternating loads in such an arrangement. This can be done by the shape or by a special type of sheathing. EP-A-0 212 243 describes a holder for a catalyst carrier body, which enables the catalyst carrier body to be tension-free elongated. In this arrangement there is only one jacket tube which concentrically surrounds the catalyst carrier body at a distance.

In many forms of catalyst carrier bodies, for example also that described in EP-A-0 245 737, it is not possible to do without a jacket tube which directly surrounds the actual honeycomb body and maintains its structure.

A honeycomb body is also known from EP-A-0 177 479, in which an inner jacket tube is arranged in an outer jacket tube in such a way that it can be freely extended.

The object of the present invention is to provide a casing for a catalytic converter which is simple and inexpensive to manufacture and which also withstands large catalytic converter bodies with a volume of, for example, more than 1 liter of thermal alternating loads.

To solve this problem, an exhaust gas catalytic converter is equipped with the features of claim 1. A inner jacket tube present for reasons of stability is surrounded approximately concentrically with an outer jacket tube. A distance of about 1 to 5 mm between the two jacket tubes is preferred. The inner jacket tube is firmly connected in an end region to the end region of the outer jacket tube, preferably welded with a circular weld seam. The other end of the inner jacket tube extends freely into the interior of the outer jacket tube and can thus expand unhindered when the temperature rises. This type of sheathing has the following key advantages:
First of all, since the inner jacket does not have to bear the internal pressure, it can be made much thinner than a simple jacket tube, for example only 0.1 to 1 mm thick. As a result of this and because of the additional outer jacket acting as thermal insulation, the inner jacket tube can warm up more quickly with the catalyst carrier body and reach a higher temperature overall than without the outer jacket. This reduces the thermal stresses inside the catalyst carrier body. Furthermore, the inner jacket tube is not exposed to any external influences, for example due to splash water, so that there is no longer any need to take this into account in the choice of material. As stated in the subclaims, a ferritic material, for example, which is optimized for this application can therefore be used. Furthermore, since it no longer fulfills any sealing function, the inner casing tube also does not have to consist of a closed sheet metal. A perforated sheet can be used, which results in considerable weight and material savings. The type, shape and size of the perforation can be varied within wide limits, but it is preferably possible to use sheets whose surface is approximately 50% provided with holes of approximately 1 cm in size.

According to the invention, the inner casing tube, provided that this has a certain axial length exceeds, additionally held in a sliding seat. This suppresses vibrations and prevents vibrations.

In particular, such a sliding seat can be formed, for example, by circumferential or individual inner beads in the outer jacket. All-round inner beads increase the stability of the outer jacket and influence its sound radiation, which can be advantageous for different applications. Advantageous embodiments are described in the dependent claims.

The outer casing tube seals the entire assembly, attaches to the rest of the exhaust system and protects against external influences, while the inner casing pipe only serves to maintain the shape and support of the actual catalyst carrier body. The outer jacket tube can preferably consist of austenitic material.

The proposed sheathing system is particularly favorable when two catalyst carrier bodies are to be accommodated in an outer casing tube. It can be useful for various reasons, e.g. B. for main catalysts of motor vehicles of the upper performance class, a given volume of, for example, about 3 liters with an outside diameter of 10 to 15 cm, not to be filled with a single catalyst carrier body, but with two or more disks arranged axially one behind the other. On the one hand, such panes can be manufactured more easily and, on the other hand, the interspaces between such panes allow the exhaust gas to swirl and thus to increase the conversion rate. It can also make sense to use disks of different axial lengths, with different numbers of channels and / or different catalytically active coatings. The embodiment according to the invention now offers a good possibility of having two catalyst disks in to arrange an outer jacket tube. As will be explained in more detail with reference to the drawing, the two inner jacket tubes of the two catalytic converter disks are each fastened, preferably welded, at one end to the two ends of the outer jacket tube. The freely extensible inner ends of the two inner jacket tubes can preferably be inserted into one another by correspondingly tapering the first inner jacket tube or expanding the second inner jacket tube accordingly. This creates a sliding seat, which slides further and further together as the arrangement heats up, thus securely holding the two catalyst carrier bodies in every operating state. Alternatively or additionally, sliding seats, e.g. B. possible by internal beads, between the outer and inner casing tubes.

Finally, the double jacket system described also enables simple integration of the entire catalyst arrangement into an exhaust system by using the usual connecting pieces at the ends, for. B. pushed onto the protruding inner jacket and can be welded to the outer jacket.

• Figur 1 eine Katalysatoranordnung aus zwei Katalysatorscheiben mit Doppelmantelsystem,
• Figur 2 eine Variante der Figur 1 mit anderer Gestaltung der Endbereiche und einer zusätzlichen Innensicke des äußeren Mantelrohres zur Abstützung des inneren Systems,
• Figur 3 eine weitere Variante der Anordnung aus Figur 1 mit zweiteiligem Außenmantel für Anordnungen mit großer axialer Länge und
• Figur 4 die Anwendung der Erfindung bei einteiligen Katalysatoren.

Exemplary embodiments of the invention in a partially schematic form are shown in the drawing and show

• FIG. 1 shows a catalytic converter arrangement consisting of two catalytic converter disks with a double jacket system,
• FIG. 2 shows a variant of FIG. 1 with a different design of the end regions and an additional inner bead of the outer casing tube to support the inner system,
• 3 shows a further variant of the arrangement from FIG. 1 with a two-part outer jacket for arrangements with a large axial length and
• Figure 4 shows the application of the invention to one-piece catalysts.

FIG. 1 shows the principle of the present invention on the basis of a large-volume catalyst which consists of two catalyst carrier bodies 1, 2. By omitting one of the two catalyst bodies and correspondingly shortening the outer jacket tube 8 in FIG. 1, however, the essence of the present invention also results when applied to one-piece catalysts, e.g. 4. The same applies accordingly to FIGS. 2 and 3.

In FIG. 1, the catalytic converter arrangement has a first metallic honeycomb body 1 and a second metallic honeycomb body 2, which are enclosed by a first inner jacket tube 3 and a second inner jacket tube 4, respectively. Both inner jacket tubes 3, 4 project beyond the actual metallic honeycomb bodies 1, 2 at both ends. The inner protruding end of the first inner jacket tube 3 has a tapered collar 6 which projects into the interior of the inner collar 7 of the second inner jacket tube 4 and forms a sliding seat 5 there. A mixing space 14 thus remains empty between the two honeycomb bodies 1, 2, in which the exhaust gases can mix again after passing through the first metallic honeycomb body 1. The outer end region of the first inner jacket tube 3 has a circumferential outer bead 13, and the outer end region of the second inner jacket tube 4 also has a circumferential outer bead 12. An outer jacket tube 8 is pushed over the entire arrangement via the two outer beads 12, 13 and fastened to the outer beads 12, 13 with circular weld seams 10, 11. The outer ends of the two inner jacket tubes 3, 4 project somewhat beyond the outer jacket tube 8, so that a connector (indicated by dashed lines) 15 can easily be pushed onto the outer jacket tube until it stops. The connection to an exhaust system of a motor vehicle can thus be carried out without any problems, under some circumstances even the weld seams 10, 11 for the simultaneous connection of connecting pieces 15, inner jacket pipes 3 or. 4 and outside Jacket tube 8 can be used. It should be added that FIG. 1 is in no way to scale, but only reflects the basic structure of the arrangement. In particular, the inner jacket tubes 3, 4 can be significantly thinner than the outer jacket tube 8. In addition, the mixing space 14 can have a much smaller axial length than shown here. It is only important that the dimensioning of the tapered collar 6 allows the pushed-on collar 7 sufficient scope for thermal elongation of the two inner casing tubes 3, 4. The honeycomb bodies 1, 2 can have different axial lengths and a different number of channels per cross-sectional unit.

As FIGS. 2 and 3 show, there are various options for connecting the inner and outer jacket and for designing the end regions of the arrangement. In addition, the honeycomb body or bodies can be supported by internal beads. Thus, FIG. 2 shows two metallic honeycomb bodies 21, 22 with their inner jacket tubes 23, 24, which, as in FIG. 1, are inserted into one another by means of a tapered collar 26 and a protruding collar 27, so that a sliding seat 25 is created. In this exemplary embodiment, the outer jacket 28 has a circumferential inner bead 20 which corresponds in depth to the space 29 between the outer and inner jacket systems. In the case of catalytic converter arrangements with a relatively long axial length, such an inner bead 20 can prevent vibrations of the honeycomb bodies 21, 22 without restricting their axial freedom of movement. Additional advantages can result from the reduction in sound radiation.

FIG. 3 shows a catalytic converter arrangement in which the outer jacket tube consists of two parts 38a, 38b which are connected to one another 38c. The connection point 38c can consist, for example, of a circumferential butt weld, but the two parts 38a, 38b can also be inserted into one another and then connected. The arrangement of the metallic honeycomb bodies 31, 32 with its inner jacket tubes 33, 34 corresponds to that of FIGS. 1 and 2. In the present case, the outer jacket tube 2 has circumferential inner beads 30a, 30b which support both inner jacket tubes 33, 34. Here, too, the collars 36, 37 of the two inner casing tubes 31, 32 slide into one another with a sliding seat 35. Figure 3 also shows two different ways of designing the end regions of the double jacket system. On the left, a connector 43 can be pushed onto the projecting end 42 of the first inner jacket tube 33 until it abuts the tapered end of the outer jacket tube 38a. On the right side, the second inner jacket tube 34 does not protrude beyond the outer jacket tube 38b. There, however, a connecting piece 41 can be pushed over the tapered end 40 of the outer casing tube 38b and connected to it. It makes sense here that no weld seams can damage the outer layers of the catalytic converter. Further variants in the design of the end regions of the arrangement are possible, the arrangements should generally be chosen such that the outer casing tube and the connecting pieces completely and tightly enclose the inner casing pipes.

For the sake of completeness, FIG. 4 shows an exemplary embodiment of the invention for one-piece catalysts. A metallic honeycomb body 51 is fixedly connected with its inner jacket tube 53 at one end to an outer jacket tube 58, with an intermediate space 59 between the two jacket tubes. A circumferential inner bead 50 in the outer jacket tube 58 holds the other end of the inner jacket tube 53 in a sliding seat 55, so that the catalyst 51 with the inner jacket tube 53 is freely extensible with respect to the outer jacket tube 58.

The present catalytic converters with double jacket system are suitable for main catalytic converters of passenger cars, particularly also for large-volume catalytic converters in the upper performance class with high thermal operating loads.

Claims (11)

1. An exhaust gas catalyst having a housing, in particular for motor vehicles, including at least one first metallic honeycomb catalyst carrier body (1; 21; 31) which is transmissive for exhaust gas with a first inner casing tube (3; 23; 33) carrying the catalyst carrier body, having the following features:

   a) there is provided an outer casing tube (8; 28; 38a, b, c) which approximately concentrically surrounds the first inner casing tube (3; 23; 33) at a spacing;

   b) the first inner casing tube (3; 23; 33) and the outer casing tube (8; 28; 38) are fixedly connected together in an end region (11, 13);

   c) the first inner casing tube (3; 23; 33) is arranged freely longitudinally extensibly in the outer casing tube (8; 28; 38a, b, c); and

   d) the freely longitudinally extensible inner casing tube (3; 23; 33) is additionally held in a sliding fit (5; 30a),

      characterised in that the sliding fit is arranged within the longitudinal extent of the outer casing tube (8; 28; 38a, b, c) and spaced from the end thereof, and in particular is formed by peripherally extending or individual internal beads (30a) in the outer casing tube (38a).
2. An exhaust gas catalyst having a housing according to claim 1, with the following features:

   a) there is provided an outer casing tube (8; 28; 38a, b, c) which approximately concentrically surrounds the first inner casing tube (3; 23; 33) at a spacing;

   b) the first inner casing tube (3; 23; 33) and the outer casing tube (8; 28; 38) are fixedly connected together in an end region (11, 13);

   c) the first inner casing tube (3; 23; 33) is arranged freely longitudinally extensibly in the outer casing tube (8; 28; 38a, b, c); and

   d) the freely longitudinally extensible inner casing tube (3; 23; 33) is additionally held in a sliding fit (5; 30a),
      characterised by the following features:

   e) disposed approximately concentrically in the outer casing tube (8; 28; 38a, b, c) is a second catalyst carrier body (2; 22; 32) having a second inner casing tube (4; 24; 34) carrying same;

   f) the first inner casing tube (3; 23; 33) is fixedly connected by its one end region to the one end region of the outer casing tube (8; 28; 38);

   g) the second inner casing tube (4; 24; 34) is fixedly connected by its one end region to the other end region of the outer casing tube (8; 28; 38a, b, c); and

   h) the other end regions (6, 7; 26, 27; 36, 37) of the first inner casing tube (3; 23; 33) and the second inner casing tube (4; 24; 34) are held with a sliding fit one within the other (5; 25; 35) and/or within (20; 30a, 30b) the outer casing tube (28a; 38a, 38b).
3. An exhaust gas catalyst according to claim 1 or claim 2 characterised in that the outer casing tube (8; 28; 38a, b, c) forms the holding means and the outer protection of the whole arrangement and is the support for the internal pressure wherein the at least one inner casing tube (3; 23; 33) only forms the secure holding bans of the catalyst carrier body (1; 21; 31).
4. An exhaust gas catalyst according to one of the preceding claims characterised in that the outer casing tube (8; 28; 38a, b, c) comprises austenitic material.
5. An exhaust gas catalyst according to one of the preceding claims characterised in that the at least one inner casing tube (3; 23; 33) comprises ferritic material.
6. An exhaust gas catalyst according to one of the preceding claims characterised in that the at least one inner casing tube (3; 23; 33) is perforated at least in portions thereof, preferably with the exception of the end regions (6, 11; 26; 36, 42).
7. An exhaust gas catalyst according to claim 2 characterised in that the second inner casing tube (4; 24; 34) also comprises ferritic and/or perforated sheet metal.
8. An exhaust gas catalyst according to claim 2 or claim 7 characterised in that the two catalyst carrier bodies (1, 2; 21, 22; 31, 32) are of different axial lengths and/or have a different number of passages per unit of cross-section.
9. An exhaust gas catalyst according to claim 2, claim 7 or claim 8 characterised in that provided between the two catalyst carrier bodies (1, 2; 21, 22; 31, 32) is an intermediate space (14) for producing turbulence in the exhaust gases and for compensating for lengthwise extension phenomena, preferably of an axial length of between approximately 1 and 3 cm.
10. An exhaust gas catalyst according to claim 2, claim 7, claim 8 or claim 9 characterised in that the two freely longitudinally extensible ends (6, 7; 26, 27; 36, 37) of the two inner casing tubes (3, 4; 23, 24; 33, 34) are guided one within the other with a sliding fit (5; 25; 35), preferably by the end (6; 26; 36) of the first inner casing tube (3; 23; 33) having a reduction portion (6) and projecting in the cold condition by a few millimetres into the interior of the second inner casing tube (4; 24; 34).
11. An exhaust gas catalyst according to one of the preceding claims characterised in that connecting portions (15; 41; 43) can be pushed on to the end regions of the overall arrangement and connected to the outer casing tube (8; 28; 38), preferably by butt welding, wherein in particular a respective single peripherally extending weld seam (10, 11) is sufficient to connect the connecting portion (15), the outer casing tube (8) and the inner casing tube (3).

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